Vapor electric converter



Dec. 5, 1939.

J. SLEPIAN VAPOR ELECTRIC CONVERTER Filed Feb. 26 1938 Fig 2 4 carbon Plates cocrbon Plates INVENTOR Joseph Slepidnj.

' ATTORNEY WITNESSES: 55ml Patented Dec. 5, 1939 varon. mrc'rmc commas. J oseph Slepian, Pittsburgh, Pa., asslgnor to westvinghouse Electric & Manul.

actnring Company,

East Pittsburgh. Pa., a corporation of Pennylvania amion February at, 193a. Serial No. 192,175

6.01allns. (Cl. 175-354) provide means for preventing excessive currents ,My invention relates, to vapor electric con- ,jverters and more particularly to means for pro- -tecting the control discharge device generally employed'in connection with the starting of such converters. a

1 With the introduction of shields, baflle plates and deflectors for minimizing backflres in vapor electric converters, the total arc dropin such converters has been increased in the order of 3 or 4 volts. Heretofore, the total are drop was composed of three main portions; namely, the drop at the anode surface, the drop at the cathode surface, and the drop in the are proper., To these potential drops may be added another, and that is the arc drop in the shields and deflectors which represents energy set free in thedischarge of ions to the surfaces, suchenergy being converted into heat. The consequent increase in the arc drop results in higher currentsflowing through the igniter circuit, which normally includes a switch and an auxilia y discharge device, such as a half-wave rectifier. An immediate eitect of unduly higher currents flowing in the igniter circuit is injury to the auxiliary devices, which arenot designed to carry such currents. It, therefore, becomes essential to maintain a higher are drop in the igniter circuit than in the converter itself to secure satisfactory operation. In the past, several auxiliary control devices terial in place of a carbon pile. The essential property is that .the cooperatingplates should be able to produce an arc withoutburning. The carbon pile contains a mimber of plates in light pressure engagement with each other connected in the igniter circuit. Due 'to the natural voltampere characteristic oi. the'carbon pile of the type I use, the arc'drop in the igniter circuit 50 may be increased to such magnitudes as may be "necessary to maintain therelative diflerences in the arcdrops between the igniter circuit and the converter itself. When the main current carrying are is established, the arc drop in the con- 55 verter is able to send only a few amperes through the igniter circuit since it will not exceed the v critical value for producing an are between the plates of the carbon pile, as well as in the aux-- .illary control davice.

: n, is, therefore, an object oi my invention to have been placed in series in the igniter circuit from flowing in the igniter circuit.

It is another object of my invention to provide means for reducing the duty on the control switch upon opening of the control circuit when such switch is used.

Still further, it is anobject. of my invention to provide an improved translating circuit, in-' cluding a vapor electric converter for protecting the igniter circuit, and which will overcome the disadvantages of prior art arrangements, and which will be simple and reliable in operation.

Anotherobject of my invention is to provide means for maintaining the relative diiference in the arc drops between the igniter circuit and the converter itself essential for successful operation.

cuit protective means may be used;

Fig. 2'is 'amodification of a converting system utilizing my protective means; and I Fig. 3 is a graphical illustration showing the volt-ampere. characteristic of. a carbon pile ac= cording to my invention.

- The apparatus'according to Fig. l of my inventtion comprises an arc discharge device 3ihaving an anode 5, a mercury pool cathode l and a starting electrode 9 of the immersion-igniter type. The cathode I and the anode 5 are externally connected to a load ll and some suitable source [3 of supply current. Suitable shields l5 and deflectors I! are mounted between the oathode l and the anode 5 for minimizing arc-backs in the discharge device 3. To initiate a discharge between the cathode I and the anode 5, a starting electrode 9, preferably one composed of some suitable material having a high resistivit such as boron carbide, is supported from the side walls 2| of the discharge device 3 and is inpermanent contactwith the'mercury cathode I.

A,co'ntrol device 28, such as a half-wave rectiher or a copper-oxide rectifier, is connected be tween the anode 5 and .the starting electrode 9 having in series with it a suitable switch 25 for opening and 'closing the startingcircult, 26. A carbon pile 21 comprising two or more discs in light pressure engagement is likewise placed in series with the'control device 23. The anode 5 of the arc discharge device 3 is connected to one side of a suitable alternating-current supply It and the cathode l to the other side in series with al'oad ll."

In the operation of 7 switch 25 is closed and alternating current is applied to -the main electrodes 5- and 1 of the converter 3. when the potential applied to the aniny device 3, the circuit circuit switch 25 and the unidirectional conductor 23 to the starting electrode 9, which initiates a cathode spot between the mercury cathode 1 and the starting electrode 9. With proper conditions of potential having been established, the cathode spot immediately expands into an arc to the anode 5 if the latter is suihciently positive. Thus, the current flowing through the starting electrode 9 is limited by the arc drop of the rectifier 23 and that of the carbon pile 21. It is essential then, that the igniter current be stopped immediately after the initiation of the main arc, and for that reason, the unidirectional conductor 23 together with the carbon' pile must have a higher are drop than that of the converter 3 itself.

Without the carbon pile 21 in'the circuit 26, the increased arc drop in the converter 3 sends a larger current through the exciting circuit 26 which continues to flow in the circuit 26 even duce an arc. The potential drop, due to the arc formed between the carbon elements added to the potential drop of the unidirectional conductor '23, is higher than the potential drop of the converter 3 itself. Consequently, if the arc in the converter 3 strikes, the lower arc drop of the converter 3 is able to send a relatively low current through the igniter circuit 26, thus reducing the duty on the auxiliary device 23. In other words, an unstable condition arises in having two series arcs'in parallel with a single arc. Hence, the lower arc drop of the converter 3 reduces the current in the igniter circuit 26 to substantially zero.

In Fig. 2, I show two converters 3 of the vapor electric type in parallel connected with opposite the igniter circuit 26, damaging the starting electrodes 3 and the unidirectional device 23.

While for purposes of illustration I have shown a certain specific embodiment of my invention, it

will be apparent to those'skilled in the art that many changes and modifications can be made therein without departing from the true spirit or scope of the appended claims.

I claim as'my invention;

1 In an electrical c onverting system, an arc discharge device comprising a plurality of main e ectrodes and an auxiliary electrode in contact with one of said main electrodes, an excitingcircuit for said device, means connected in said exciting circuit for interrupting current flow,

ode 5 is positive, current will flow through the means including a plurality of cooperating carbon plates in series with said interrupting means, and means for maintaining said carbon plates an are between said starting electrode and said cathode, a unidirectional conductor in said circuit means, means for preventing abnormal currents from flowing throughsaid unidirectional conductor including a pile of cooperating carbon plates connected in said circuit means, and means .for maintaining said carbon plates in light pressure engagement with each other to maintain the potential drop in said circuit means higher than in said converter.

3. The combination with a load, an alternatingcurrent source and a vapor electric converter connected thefito, circuit means for starting said converter, means connected in said circuit means for rendering said converter alternately conductive and non-conductive, means including a group of cooperating carbon plates connected in said circuit means for maintaining a predetermined relationship between the potential drops in said converter and said circuit means, and means formaintaining said carbon plates in light pressure engagement with each other.

4. In a vapor electric converting system comprising a plurality of vapor converters each having a plurality of principal electrodes and a starting electrode in contact with one of said principal electrodes, a connection between saidstarting electrodes, a switch in said connection, a group of cooperating carbon plates in series with said switch, and means for maintaining said carbon plates in loose-fitting engagement to increase the potential drop through said plates during the flow of excessive current therethrough.

5.- In an electrical conversion system having an arc discharge device comprising a plurality of main electrodes and an auxiliary electrode in contact with one of said main electrodes, an exciting circuit connected to said auxiliary electrode for initiating an arc in said device, a uniare discharge device comprising a plurality of main electrodes and an auxiliary electrode in.

contact with oneof'said main electrodes, an exciting circuit connected to said auxiliary electrode forinitiating an arc in said device, a, unidirectional current-carrying device in said exciting circuit, a pile of cooperating carbonaceous 1 blocks having a non-linear volt-ampere characteristic connected in series with said unidirectional current-carrying device, said carbonaceous blocks beingmounted in loose fitting engagement with each other so that the contact area be-f tween the blocks is very small whereby the potential drop through said pile is increasedduring the flow of excessive currents therethrough'.

JOSEPH SLEPIAN. 

